# Method for forming and checking of message certified with watermark

FIELD: computer science.

SUBSTANCE: previously for sender and receiver a binary series of digital watermark k-bit long is formed as well as binary series of secret key, message is certified at sender side using binary series of digital watermark and secret key, certified message is sent to receiver, where authenticity of received message is checked using binary series of digital watermark and secret key.

EFFECT: higher reliability, higher efficiency.

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The invention relates to the field of telecommunications and information technologies, specifically to techniques for the protection of the authenticity of the message, such as converted to digital mind speech, sound, music, television, Fax, etc. messages. Under original message means the message that there are no unauthorized changes its content and identified its sender (author). Unauthorized alteration of the content and authorship of messages can be done by the attacker in the process of transmission and storage generated by the sender of the message. The task of the receiver of the message is to establish the fact that the content of the received message matches the content transmitted by the sender of the message and that the received message is the sender. The technical result achieved during the implementation of the claimed technical solution is the development of a method of forming and verifying digitally watermarked messages, providing increased security messages digitally watermarked sender, from the deliberate actions of the attacker to modify the message content and authorship.

The proposed method of generating and verifying digitally watermark message can be used in the IAOD to establish the authenticity of the speech, sound, music, television, Fax, etc. multimedia messages transmitted and stored in modern telecommunication systems. Converted by the sender to the digital multimedia information during transmission and storage can easily be changed by the attacker, and in a modified form sent to the recipient. This strategy of the attacker is called spoofing attack messages. Also the attacker, without waiting for transmission of a legitimate sender of a message can be regenerated to form a false message and on behalf of the sender to send it to the recipient. This strategy of the attacker is called the attack simulation messages. In addition, the attacker can intercept the transmitted legitimate sender of the message and to change the signature of the sender on their own, appropriating the right of authorship of this message. This strategy of the attacker is called spoofing attack author of the message. Listed attacker easily implemented on digital multimedia messages using common audio, video, graphics and other editors. The recipient distorted information may not reveal the fact that the distortion of the content and authorship. Therefore, for speech, sound, music, television, facsimile the x etc. messages transmitted via communication channels or recorded on such media as audio or video tapes, CDS or DVDs, floppy disks, etc. that you want to install the absence of deliberate distortions and their authorship.

Known methods of establishing the authenticity of multimedia messages, recorded on audio or video cassettes, CDS and floppy disks. These methods use a unique technological characteristics of the media. For example, the authenticity of the message set if the reader detects the disk carrier protected messages in the correct place the label in the form of bad sectors. Known methods of establishing the authenticity of multimedia messages, recorded on audio or video cassettes, CDS and floppy disks are described, for example, in the book: Yelnikov. Cryptography from papyrus to your computer. - ABF, 1996, page 218. However, the authentication message based on the use of unique technological characteristics of these media messages are fundamentally unable to install the absence of these messages deliberate distortions and their authorship when they are overwritten with the media, with a unique technological features, on the media, these signs do not have.

Therefore, ways of establishing the authenticity of media messages must be built on the basis of embedding the message information to the authentication not using any reference to the unique technology or other characteristics of these media messages. Such methods have recently been created in the framework of the steganographic methods of information protection and became known methods of forming and testing certified digital watermark message. These methods are described, for example, in the book: Weggemann, Innoko, Ivina. Digital steganography. M: salty-R, 2002, page 6-17. The main idea of these methods is to embed to assure a multimedia message a special label - digital watermark (DWM) of the sender (author) message using the secret key. This CEH is a unique identifier of the sender and uniquely identifies the sender of the message when retrieving the recipient of this CEH from a received message using a secret key. The fact extract this CEH from a received message using a secret key also allows the recipient to verify that the contents of the certified data of the watermark message has not been altered and is not formed as a result of malicious acts. By analogy with watermarks, which attests to the authenticity of banknotes on paper, these identifiers received the name of a digital watermark message. Digital watermarks soo what claims can be visually perceived, for example, the image of a registered trademark of the manufacturer or the facial image of the sender, and are not visually perceived, for example, the binary sequence registered as personal identification number (PIN) of the sender of the multimedia message.

Embedding assure a multimedia message, a digital watermark sender is possible using a secret key unknown to a potential attacker. The validation phase of a received multimedia message using the same secret key is extracted digital watermark, which slychaetsya with digital watermark message sender, and when they match, the decision about the authorship of this message and lack of distortion. An attacker who knows the digital watermark of the message sender, but does not know its secret key, not able to form a multimedia message, digitally watermarked this sender that when checking the recipient acknowledges genuine.

Known methods of forming and verifying digitally watermarked messages are described, for example, in the book: N. Johnson, S. Jajodia "Steganalysis of Images Created Using Current Steganographic Software".// Proceeding of the Workshop on Information Hiding, 1998. They are in the preliminary formation of the years for the sender and recipient of the binary sequence of digital watermark length of 64 bits. The binary sequence of digital watermark is the same for any assure the sender of the multimedia message. To authenticate the sender of the message, starting with the first count, the next timing of the messages read in the next block of samples of length 64 counts. The next block of samples transform method in discrete cosine transform in 64 coefficient discrete cosine transform. The values of the coefficients are rounded to whole numbers. From the first to the last bit, read the i-th bit, where i=1, 2,...,64, binary sequence of digital watermark. From the first to the last coefficient of the discrete cosine transform read another factor, in which the least significant bit is replaced by the i-th bit of the binary sequence of the digital watermark, the converted value of the next coefficient discrete cosine transform reads in the next output block of coefficients of length 64 ratio. On completion of the next output block of coefficients it is converted by way of the inverse discrete cosine transform in 64 counts of the next block certified message that is passed to the recipient. Read the next 64 counts messages and re-read the last binary is a sequence of digital watermark and perform the subsequent steps until while doing the regular timing of the message. For authentication is received by a receiver of the message, starting with the first reference adopted by the next timing messages read in the next block of received samples of length 64 counts. The next block of received samples transform method in discrete cosine transform in 64 received coefficient discrete cosine transform. Values taken coefficients are rounded to whole numbers. From the first to the last bit, read the i-th bit, where i=1, 2,...,64, binary sequence of digital watermark and, from the first to the last adopted another coefficient discrete cosine transform, in which the least significant bit is compared with the i-th bit of the binary sequence of the digital watermark. If all the least significant bits received another factors coincided with the relevant i s bits of the binary sequence of the digital watermark, then the next block of received samples is considered genuine. Then the following received timing messages read in the next block of received samples of length 64 counts, then repeat the steps for verifying that the next block of received samples up until act adopted by the next timing of the message.

In the known methods of development is the development and validation of digitally watermarked message replacing the least significant bits of the next coefficients of the discrete cosine transform of the next block of samples at the i-th bits of the binary sequence digital watermark leads to a small change in the value of the next timing messages from this block. If, for example, digitally watermark message is a grayscale image, these methods create and verify digitally watermarked messages lead to relatively small changes in the brightness of each of the 64 pixels of the next block of the image that is visually unobtrusive and almost does not reduce the image quality.

A disadvantage of the known methods of forming and verifying digitally watermark message is a low security messages that are digitally watermarked sender, from the deliberate actions of the attacker to modify the message content and authorship.

When the deliberate altering the contents of the message, digitally watermarked sender, an attacker can modify any bits of the next coefficients of the discrete cosine transform regular blocks of samples of this message, except the least significant bits of these coefficients. Since the least significant bits of the next coefficients of the discrete cosine transform regular blocks of samples of the modified messages are not modified by the attacker, then the recipient of the modified message, performing the written review actions, mistakenly recognizes the received message is authentic. Thus, the attacker has the ability to customize the message, digitally watermarked sender, a fake message. Therefore, known methods do not provide protection messages, digitally watermarked sender to the spoofing attack messages.

In another strategy, an attacker who knows at least one arbitrary message, digitally watermarked sender can generate profitable him a false message, and the least significant bits of the next coefficients of the discrete cosine transform regular blocks of samples of this communication is to replace the corresponding bits of the binary sequence of digital watermark legitimate sender. When checking the recipient of the authenticity of the received message, the least significant bits of the next coefficients of the discrete cosine transform of the next block of samples received message match the corresponding bits of the binary sequence of the digital watermark of the sender, i.e. the recipient received a false message will mistakenly be considered genuine. Thus, the attacker has the opportunity on behalf of the sender successfully to impose on the recipient arbitrary false reports. Sledovatel is, known methods do not provide protection messages, digitally watermarked sender to attack simulation messages.

In the third strategy, the attacker can replace the least significant bits of the next coefficients of the discrete cosine transform of regular units of counts messages that are digitally watermarked sender to the corresponding bits of the binary sequence a digital watermark, without changing other bits of the next DCT coefficients. The attacker, as well as the legitimate sender may be the same potential author of a message in the information and telecommunication system and in accordance with previously known methods for the attacker to generate a unique binary sequence of digital watermark. The recipient of the message with the modified authorship, fulfilling described in the known methods the verification steps using binary sequence of digital watermark attacker, mistakenly recognizes the author of a received message, the attacker. Thus, the attacker is able to assign the authorship of an arbitrary message to the legitimate sender. Therefore, known methods do not provide protection messages, certified digital water testing the Ohm sender the spoofing attack authorship.

The closest in technical essence to the claimed method of forming and testing certified digital watermark message is the method described in U.S. patent 5613004 IPC^{6}H 04 L 009/20 from 18.03.97. Prototype method of forming and testing certified digital watermark message is in the preliminary formation of the sender and recipient of the binary sequence tags digital watermark of length m bits of the binary sequence of digital watermark length of k bits and the binary sequence of the secret key length of k bits. Pre-set the number of matching bits of the binary sequence tags digital watermark and the number of matching bits of the binary sequence a digital watermark in a zero value. To authenticate the sender of the message, from the first to the m-th symbol, read the next bit of the binary sequence tags digital watermark and the binary sequence of the next reference message. In the binary sequence of the next reference message bit is replaced by the next bit of the binary sequence tags digital watermark and the converted binary sequence of the next reference message is passed to the recipient in which the quality certified.
Then sequentially reads the i-th, where i=1, 2,...,k bits of the binary sequence of the secret key, the i-th bit of the binary sequence of the digital watermark and the binary sequence of the next reference message. If the i-th bit of the binary sequence of the secret key accepts a single value, then the low-order bit of the binary sequence of the next reference message is replaced by the i-th bit of the binary sequence of the digital watermark and the converted binary sequence of the next reference message is passed to the recipient as certified. If the i-th bit of the binary sequence of the secret key takes the value zero, the binary sequence of the next reference message without changing the transfer to the recipient as certified. Then again, from the first to the m-th symbol, read the next bit of the binary sequence tags digital watermark and the binary sequence of the next reference message and perform the subsequent action up until the coming of the binary sequence of the next timing of the message.

For authentication is received by the message recipient reads the adopted binary sequence of the next reference message and, from the first to the m-th symbol, next is it binary sequence tags digital watermark. The low-order bit of the adopted binary sequence of the next reference message is compared with the next bit of the binary sequence tags digital watermark, and when they match match number of bits of the binary sequence tags digital watermark increase on a single value, otherwise this number is set to zero and reads the adopted binary sequence of the next reference message and re-read, from the first to the m-th symbol, the next bit of the binary sequence tags digital watermark and perform the subsequent steps. If the number of matching bits of the binary sequence tags digital watermark has reached the value of m, the reading adopted by the binary sequence of the next reference message and the i-th, where i=1, 2,...,k bits of the binary sequence of the secret key and the i-th bit of the binary sequence of the digital watermark. If the i-th bit of the binary sequence of the secret key is equal to a single value, then the low-order bit of the adopted binary sequence of the next reference message is compared with the i-th bit of the binary sequence of the digital watermark, and when they match match number of bits of the binary sequence of digital watermark increase on a unit is the value after reading the k-th bit of the binary sequence of the digital watermark, the number of matching bits of the binary sequence of digital watermark is compared with the number of singular values of the bits of the binary sequence of the secret key and in equality adopted by the binary sequence m+k regular times, the message is considered authentic, and then repeat the steps for authentication of the next group of m+k received another message counts prior to the completion of reception of all samples of the message.

The disadvantage of the prototype of the claimed method of forming and testing certified digital watermark message is a low security messages that are digitally watermarked sender, from the deliberate actions of the attacker to modify the message content and authorship. When the deliberate altering the contents of the message, digitally watermarked sender, an attacker can modify any bits except bits, an arbitrary number of regular samples of the certified message. As the lower bits of the next samples of the modified messages are not modified by the attacker, then the recipient of the modified message, performing the steps of checking, mistakenly recognizes the received message is authentic. Thus, the attacker has the ability to customize the message, digitally watermarked sender, a fake message. Therefore, the prototype of the claimed method does not provide protection messages, digitally watermarked sender to the spoofing attack messages.

In another strategy, an attacker who knows the binary sequence of digital watermark sender can generate a false message, consisting of regular counts, and lower bits of the binary sequence of regular counts of false alarms be replaced by lower bits of the binary sequence of the next timing messages, digitally watermarked sender. The recipient of such false messages, performing the steps of checking, mistakenly recognizes the received message is authentic. Thus, the attacker has the opportunity on behalf of the sender successfully to impose on the recipient arbitrary false reports. Therefore, the prototype of the claimed method does not provide protection messages, digitally watermarked sender to attack simulation messages.

In the third strategy, the attacker can replace the lower bits of the binary sequence of the next timing messages, digitally watermarked sender, the next bits of the binary sequence is its label digital watermark and successive bits of the binary sequence a digital watermark. If the attacker keeps unchanged the rest of the bits of the binary sequence of the next timing of the message, i.e. the message content does not change. The attacker, as well as the legitimate sender may be the same potential author of a message in the information and telecommunication system in accordance with the prototype of the proposed method for pre attacker to generate a unique binary sequence tags digital watermark length of m bits, the binary sequence of digital watermark length of k bits and a bit string of the secret key length of k bits. The recipient of the message with the modified authorship, fulfilling described in method-prototype review actions using the binary sequence tags digital watermark of length m bits of the binary sequence of digital watermark length of k bits and the binary sequence of the secret key length of k bits, an attacker would erroneously recognize the author of a received message, the attacker. Thus, the attacker is able to assign the authorship of an arbitrary message to the legitimate sender. Therefore, the prototype of the claimed method does not provide protection messages, digitally watermarked sender to the spoofing attack authorship.

When all is written deliberate actions of the attacker does not require knowledge of the binary sequence of the secret key length of k bits.

The above drawback of the prototype of the claimed method of forming and verifying digitally watermarked messages arose from the fact that embedded in the message is the binary sequence of the digital watermark does not depend on the assure of the message and the binary sequence of the secret key.

The aim of the invention the claimed technical solution is to develop a method of generating and verifying digitally watermarked messages, providing increased security messages digitally watermarked sender, from the deliberate actions of the attacker to modify the message content and authorship.

This objective is achieved in that in the known method of forming and testing certified digital watermark message, which consists in the preliminary formation of the sender and recipient of the binary sequence of digital watermark length of k bits and a binary sequence of a secret key to verify the sender of the message using binary sequences of digital watermark and secret key. Transmit a certified message to the recipient, where authenticates the received message using binary sequences of digital watermark and secret what about the key,
additionally previously for the sender and receiver form a hashing function with a binary output value and set the minimum number of K_{min}authentic samples of messages within a group of k consecutive received. The minimum number of K_{min}authentic samples of messages within a group of k consecutive received set of conditionswhere R_{under}allowable probability of making a genuine group of k regular counts of the messages, which is not true.

To authenticate the sender of the message sequentially reads the i-th, where i =1, 2,...,k-bit binary sequence of digital watermark and the binary sequence of the next reference message, which hairout using a binary sequence a secret key in a pre-formed hash functions. Then compare the hash value with the i-th bit of the binary sequence of the digital watermark, and when they match the binary sequence of the next reference message is passed to the recipient as certified, and if not binary sequence of the next reference message consistently transform by changing the low-order bits. To convert a binary sequence PTS is Reden reference message by changing the bits sequentially change her one,
two, three and so on to the least significant bits. Then after each conversion the converted binary sequence of the next reference message hairout using a binary sequence a secret key in a pre-formed hash functions, compare the hash value with the i-th bit of the binary sequence of the digital watermark, and converting the binary sequence of the next reference message perform to match the hash values of the converted binary sequence of the next reference message from the i-th bit of the binary sequence of the digital watermark, and then converted to a binary sequence of the next reference message is passed to the recipient as certified. After certification of the binary sequence of the next reference message using the k-th bit of the binary sequence of digital watermark again, from the first to k-th, read the i-th bit of the binary sequence of the digital watermark, and the binary sequence of the next reference message and perform the subsequent action up until the coming of the binary sequence of the next timing messages. The recipient of the message previously from the number at imaamah binary sequences of the next timing messages secrete reference
corresponds to the first bit of the binary sequence of the digital watermark from the sender of the message. For selecting the next reference message, corresponding to the first bit of the binary sequence of the digital watermark from the sender of the message, a pre-set maximum value of the probability P_{Osh}erroneous selection of reference adopted by the recipient of the binary sequence of the next timing messages hairout using a binary sequence a secret key in a pre-formed hash functions, hashed values are compared sequentially with the appropriate, starting with the first, the values of the bits of the binary sequence of digital watermark before reaching m their matches in a row, whereand the actionmeans rounding values-log_{2}P_{Osh}to the nearest integer, and the corresponding first bit of the binary sequence of the digital watermark from the sender of the message take the first sample of k consecutive received binary sequence of the next timing of the message.

Then the authentication is accepted by the recipient of the message consistently take k binary posledovatelno is it regular counts messages
hairout them using a binary sequence a secret key in a pre-formed hash functions and each i-th hash value is compared with the i-th bit of the binary sequence of the digital watermark. Calculate the number of K_{c}hashed binary sequences ordinary times, the message of the k received samples, which coincided with the values of corresponding bits of the binary sequence of the digital watermark, and when K_{with}≥_{min}taken k binary sequences ordinary times, the message is considered authentic, and then repeat the steps for authentication of the next group of k binary sequences ordinary times, messages and so on until completion of reception of all binary sequences of the next timing of the message.

Specified a new set of actions performed due to unpredictable to an attacker according to all the bits in the binary sequence of the next timing certified digital watermark message from the corresponding bits of the binary sequence of digital watermark length of k bits and the binary sequence of the secret key allows you to increase the security of the message, digitally watermarked sender to intentional action is Lomachenko to change the message content and authorship. This unpredictability in unknown attacker binary sequence a secret key provided by hashing the binary sequence of the next reference message using a binary sequence a secret key in a pre-formed hash functions with binary output value. Pre-formed hash function with a binary output value to an attacker is indistinguishable from a random function, i.e. the probability of correct identification of its output value when an unknown to an attacker binary sequence of a secret key is equal to ½, that is equal to the probability of random guessing.

Pre-formed hash function with a binary output value must satisfy the following requirements:

1) Binary output value of the hash functions equally dependent on each bit of the binary sequence of the next message counts and each bit of the binary sequence of the secret key.

2) Knowing the description of the hash functions and the binary sequence of the next timing certified messages, an attacker is not able to calculate the binary sequence of the secret key.

3) Knowing the description of the hash function, the attacker does not str is Aubin correctly to form the output value of the hash function with probability significantly greater ½ for binary sequences of regular samples selected messages, without knowing the binary sequence of the secret key.

When an unknown attacker binary sequence of the secret key, he can not certified by the sender of the digital watermark message to change the regular timing of the message so that the recipient of the modified message, performing the steps of checking, wrongly recognized received message is authentic. When the attacker one another certified reference message, the probability that the hash value of the binary sequence modified by an attacker one of the next reference message matches the corresponding bit of the binary sequence a digital watermark, as well ½. In a group of k consecutive received samples of the messages for the recognition of their true should equal no less than To_{min}hashed values binary sequences modified by an attacker regular counts of the messages with the corresponding bits of the binary sequence of the digital watermark. Therefore, the probability of making a genuine group of k regular counts of the messages, which is not genuine, equal. By choosing the appropriate values of K_{min}you can provide the e arbitrarily small allowable probability P_{
SS}when considering the spoofing attack messages. For example, when K_{min}=20 the probability of a successful attack spoofing messages does not exceed one million: P_{SS}≤2^{-20}. Therefore, this new set of actions allows you to increase the security of the message, digitally watermarked sender to the spoofing attack messages.

Also, when an unknown attacker binary sequence of a secret key and a known one or more messages that are digitally watermarked sender, an attacker cannot re-form the not genuine message that consists of binary sequences ordinary times, so that the recipient is not genuine message, performing the steps of checking, wrongly recognized received message is authentic. When forming the attacker a false message of length k of the next times the probability that at least K_{min}hashed values binary sequences ordinary times, not genuine messages will coincide with the corresponding bits of the binary sequence of the digital watermark, is. Therefore, the probability of making a genuine group of k regular counts of the messages, which is not genuine, equalWyborem the corresponding values of K_{
min}you can provide an arbitrarily small probability P_{SS}when this attack simulation messages. For example, when K_{min}=30, the probability of a successful attack simulation messages does not exceed one billion. Therefore, this new set of actions allows you to increase the security of the message, digitally watermarked sender to attack simulation messages.

Also, when an unknown attacker binary sequence of a secret key and a known message, digitally watermarked sender, the attacker cannot change the authorship of the message on his own. Let the attacker, as the sender is the same potential by the author of the message and in accordance with the stated way before the attacker can form a unique binary sequence of digital watermark length of k bits and a bit string of the secret key. When you change the author of the message, the attacker in each binary sequence of the next reference message, digitally watermarked sender has several least significant bits, for which the recipient verifies the digital watermark sender, replace with the appropriate number of least significant bits, in which is embedded C is proveu watermark of the attacker. This certified message is distorted in several least significant bits of the binary sequence of each of the next reference message. The quality of voice, sound, music, television, facsimile and other communication transmitted via a communication channel or stored on devices such as audio or video tapes, CDS or DVDs, floppy disks, etc. becomes significantly worse. The goal of the attacker in the attack spoofing authorship is assigning itself the copyright and property rights on the message while maintaining the required quality of the message. For example, if the attacker has replaced recorded on VHS video brand trademark manufacturer on your own, but there were noises, clearly perceived by the organs of sight and hearing of the viewer, the assignment of authorship and reproduction for the purpose of selling such counterfeit products has no meaning. Therefore, this new set of actions allows you to increase the security of the message, digitally watermarked sender to the spoofing attack authorship.

Conducted by the applicant's analysis of the level of technology has allowed to establish that the analogs are characterized by the sets of characteristics is identical for all features of the claimed method of forming and verifying digitally leading the th sign messages no. Therefore, the claimed invention meets the condition of patentability "Novelty".

Search results known solutions in this and related areas of technology in order to identify characteristics that match the distinctive features from the prototype features of the claimed invention, have shown that they do not follow explicitly from the prior art. Of certain of applicant's prior art there have been no known impact provided the essential features of the claimed invention to the achievement of the technical result. Therefore, the claimed invention meets the condition of patentability "Inventive step".

The claimed method is illustrated by figures that show:

- figure 1 - timing diagram of formation of the certified digital watermark message;

- figure 2 is a typical example of the results of the hash binary sequence of the next timing messages using the binary sequence a secret key in a pre-formed hash functions;

- figure 3 - timing diagram of checks received message, out relative to digitally watermark message;

on the figure 4 - timing diagram of checks received message, synchronized consider is Ino certified digital watermark message;

- figure 5 is graphs showing the effect of the proposed method.

The implementation of the inventive method consists in the following.

To protect the authenticity of the multimedia message that is transmitted on modern information and telecommunication networks, the binary sequence of the next timing messages using a binary sequence of a secret key embedded information control authentication, called digital watermark message. View the binary sequence of the secret key shown in figure 1(a). Singular values of the bits in the figures is shown as a hatched pulses, zero bits in the form of not shaded pulses. To the binary sequence of the secret key must meet the requirement cannot be computed by the attacker, which can be well-known certified with his message. View binary sequence of digital watermark of length k bits is shown in figure 1(b). The binary sequence of the digital watermark message sender is registered as a unique identifier of the message sender and the fact of its detection in a received message using the secret key of the sender in the accepted message clearly indicates the authorship of the message sender, which is owned by this digital watermark, and the absence of distortion in a received message. The binary sequence of digital watermark sender (author) messages may be known.

The original message, such as speech, audio, video, facsimile and the like, the view of which is shown in figure 1(b), before they are certified digital watermark pre-convert to digital mind, for example, by the method of pulse-code modulation (PCM). Known methods of converting speech, audio, video, facsimile, etc. messages to the digital kind is described, for example, in the book: Agua, DSI, Mevaseret, Limping "Theory of signal transmission". - M.: Radio and communication, 1980, page 243. Known methods of transformation can be performed in two stages: first, perform sampling and quantization, and then discretized and quantized signal is converted into a binary sequence of the next timing of the message.

Kind of digital voice, audio, video, facsimile and similar messages, discretized with sampling frequency F=1/T, where T is the time interval between successive samples, and is quantized to q levels (q=256) is shown in figure 1(d). The first sample is set equal to 179, the second reference - 185 k-th reference - 180, etc. kind of binary sequences ordinary times, the message shown in figure 1(d). When q=256 binary follower of the spine of the next timing messages consist of 8 bits. The most significant bit sequence write first (on the left in figure 1(d), LSB write the last in the sequence (on the right in figure 1(d).

Known methods of forming and verifying digitally watermark message bit-embed binary sequence a digital watermark in the least significant bits of the sequence of samples of the messages that are described, for example, in the book: Aspromonte. Statistical method for the detection of steganographic hiding information in audio files: materials of the International Informatization forum IIF-2000, - M.: ZAO "Informsvyazizdat", 2000, s-204. Embedding binary sequence a digital watermark in the least significant bits of the sequence of samples of speech, audio, video, facsimile and similar messages does not deteriorate quality assure messages.

Attackers can try to break the built-in certified multimedia message, a digital watermark or make them find ways to verify a digital watermark. If an attacker managed to destroy the embedded digital watermark or make it is not detected, then it can impersonate the legitimate author of such a multimedia message.

To determine the sample number of the message, starting with the otorongo when checking a digital watermark, you must start the extraction of the binary sequence of the digital watermark, in the known methods of forming a digital watermark to actually embed a digital watermark message is embedded binary sequence tags digital watermark. If the scan digital watermark in the message identified by the binary sequence tags digital watermark, clearly defined start the built-in message of the binary sequence of the digital watermark.

Therefore, if the attacker will be distorted samples of the certified message in which is embedded a binary sequence tags digital watermark verification of a digital watermark label will not be detected and consequently, the digital watermark will not be read. The binary sequence tags digital watermark is usually well-known, can easily be detected and distorted by an attacker in a certified message. Increasing resilience to deliberate actions of the attacker can be achieved if you do not use a special binary sequence tags digital watermark to determine the beginning of the built-in message of the binary sequence of the digital watermark on the binary values of a digital watermark using a known recipient DV the primary sequence of the secret key.

If you will be distorted samples of the certified message in which is embedded a binary sequence of a digital watermark, in the known methods when checking extracted from the certified message binary sequence of digital watermark will not be identified with a binary sequence of digital watermark of the author (sender) of the message, because they require their matches accurate to bits. Therefore, increasing resilience to deliberate actions of the attacker can be achieved if you use the digital watermark, which can be identified with the digital watermark of the author (sender) of the message in the presence of distortion in one or more samples of the certified message.

In the proposed method to ensure the formation and verification of digitally watermarked message, adds security messages digitally watermarked legitimate sender, to the deliberate actions of the attacker to change the content of the message and its authorship is implemented by the following sequence of actions.

Preliminary formation for the sender and recipient of the binary sequence of the digital watermark of length k bits is as follows. Choosing a unique digital watermark will send what I have.
A unique binary sequence of digital watermark of length k bits of the sender form a random sequence of binary symbols, described, for example, in the book: D. Knuth "the Art of computer programming on the computer". - M.: Mir, 1977, volume 2, page 22. When random binary sequence of digital watermark sender 32 bits long, the probability of matching with a binary sequence of digital watermark of another sender is equal to 2^{-32}≈10^{-9}that is almost enough to ensure nepovtorimosti digital watermark large number of senders.

Preliminary formation for the sender and recipient of the binary sequence of the secret key is as follows. The binary sequence of the secret key form a random sequence of binary symbols, described, for example, in the book: Knut "the Art of computer programming on the computer". - M.: Mir, 1977, volume 2, page 22. The length of the binary sequence of the secret key must be at least 64 bits, which is described, for example, in the book the book Mdeed, Dkent "the data encryption Standard: Past and future". TIER, 1988, - t, No. 5, page 45.

Preliminary formation for the sender and recipient hash functions with binary output value is as follows. Known the ways of pre-formation of the hash functions described, for example, in the book Mdeed, Dkent "the data encryption Standard: Past and future". TIER, 1988, - t, No. 5, page 49. They consist in the formation of the hash function with a secret key, using the encryption algorithm DES in feedback mode to text mode or output feedback. However, these methods prior to the formation of hash functions form hash functions with output value of length 64 bits. Therefore, for the preliminary formation of hash functions with a binary output value is proposed output value of length 64 bits of hash functions, is formed in the known methods, to convert the computation modulo 2. The result of this transformation, the even-numbered output values of length 64 bits will take zero values, and the odd-numbered output values of length 64 bits will accept a single value. Convert binary sequence by calculating the modulo 2 is described, for example, in the book Baselabel "Microprocessors and their application in transmission systems and signal processing". - M.: Radio and communication, 1988, page 10.

Preliminary determination for the sender and recipient the minimum number To_{min}authentic samples of messages within a group of k consecutive received is as follows. The minimum number of K_{min}true the count of messages in a group of k consecutive received set equal
where R_{under}allowable probability of making a genuine group of k regular counts of the messages, which is not true. For example, the amount of allowable probability of making a genuine group of k regular counts of the messages, which is not true, set to P_{under}=2^{-32}that is recommended in the book Gsimmons "Review of methods of authentication information". TIER, 1988, - t, No. 5, page 116. Therefore, the value of K_{min}it is advisable to install at least 32.

To authenticate the sender of the message using binary sequences of digital watermark length of k bits and a secret key sequentially reads the i-th, where i=1, 2,...,k-bit binary sequence of digital watermark and the binary sequence of the next reference message. Known methods sequential reads of bits of the binary sequence of the digital watermark and the binary sequence of the next reference message is described, for example, in the book Baselabel "Microprocessors and their application in transmission systems and signal processing". - M.: Radio and communication, 1988, page 70.

Read the binary sequence of the next reference message hairout using a binary sequence a secret key in a pre-formed functions hachirobei is. For this binary sequence of the next reference message encrypts the data encryption algorithm DES-mode feedback text using the binary sequence of the secret key. The data encryption algorithm DES-mode feedback text using the binary sequence of the secret key are described, for example, in the book Mdeed, Dkent "the data encryption Standard: Past and future". TIER, 1988, - t, No. 5, page 49. Then the output value of length 64 bits of hash functions transform computation modulo 2. Converting the output value computation module 2 is described, for example, in the book Baselabel "Microprocessors and their application in transmission systems and signal processing". - M.: Radio and communication, 1988, page 10. The result of this transformation hash value takes a value of zero even when the output values are 64 bits long, and takes a value of unity when the odd-numbered output values of length 64 bits.

The figure 2 shows a typical example of the results of the hash binary sequence of the next timing messages using the binary sequence a secret key in a pre-formed hash functions. The binary sequence of the next timing messages, and the converted binary PEFC is the regular sequences of samples of the message match the values of the next message counts from 0 to 255. Hash value of the binary sequence of the next message counts accept zero or a single value with probability close to 1/2.

Then compare the hash value of the binary sequence of the next reference message with the i-th bit of the binary sequence of the digital watermark. Known methods of comparing the hash value of the binary sequence of the next reference message with the i-th bit of the binary sequence of digital watermark is described, for example, in the book: Writercon, Auldon "error-correcting Codes". M.: Mir, 1976, page 52. The result of the comparison may be a match or mismatch. When matching hash values with the i-th bit of the binary sequence of digital watermark binary sequence of the next reference message is passed to the recipient as certified. How to transfer to the recipient as a certified binary sequence of the next reference message known and described, for example, in the book: Agua, DSI, Mevaseret, Limping "Theory of signal transmission". - M.: Radio and communication, 1986, page 11.

An example of the obtained hachirobei values is shown in figure 1(e). Let hashing the binary sequence of the first reference message formed of a single hash value. who but compared with the value of the first bit of the binary sequence of the digital watermark, and when they match the binary sequence of the first reference message is passed to the recipient as a certified binary the sequence of the first reference message. Example certified binary sequences ordinary times, the message shown in figure 1(l).

If this does not match the binary sequence of the next reference message consistently transform by changing the low-order bits. To convert the binary sequence of the next reference message by changing the bits sequentially change it one, two, three and so on to the least significant bits. Sequential change of one, two, three and so on to the least significant bits of the binary sequence of the next reference message can be made consistent by inverting one, two, three and so on to the least significant bits of the given binary sequence. Known methods by inverting one, two, three and so on to the least significant bits of the binary sequence of the next reference message is described, for example, in the book Baselabel "Microprocessors and their application in transmission systems and signal processing". - M.: Radio and communication, 1988, page 19.

After each conversion the converted binary sequence of the next reference message hairout using a binary sequence a secret key in a pre-formed hash functions, cf is more of a hash value from the i-th bit of the binary sequence of the digital watermark, moreover, the transformation of the binary sequence of the next reference message perform to match the hash values of the converted binary sequence of the next reference message from the i-th bit of the binary sequence of the digital watermark, and then converted to a binary sequence of the next reference message is passed to the recipient as certified.

To hash with binary sequence a secret key in a pre-formed hash functions converted binary sequence of the next reference message encrypts the data encryption algorithm DES-mode feedback text using the binary sequence of the secret key. The data encryption algorithm DES-mode feedback text using the binary sequence of the secret key are described, for example, in the book Mdeed, Dkent "the data encryption Standard: Past and future". TIER, 1988, - t, No. 5, page 49. Then the output value of length 64 bits of hash functions transform computation modulo 2. The result of this transformation hash value takes a value of zero even when the output values are 64 bits long, and takes a value of unity when the odd weekend meant the s of length 64 bits.

Then compare the hash value of the converted binary sequence of the next reference message with the i-th bit of the binary sequence of the digital watermark. Known methods of comparing the hash value with the i-th bit of the binary sequence of digital watermark is described, for example, in the book: Writercon, Auldon "error-correcting Codes". M.: Mir, 1976, page 52. When matching hash values with the i-th bit of the binary sequence of digital watermark last converted binary sequence of the next reference message is passed to the recipient as authenticated, otherwise continue to convert the binary sequence of the next reference message. How to transfer to the recipient as a certified converted binary sequence of the next reference message known and described, for example, in the book: Agua, DSI, Mevaseret, Limping "Theory of signal transmission". - M.: Radio and communication, 1986, page 11.

An example of the obtained hachirobei values is shown in figure 1(e). Let, as shown in figure 1(e), if the hash of the binary sequence of the second reference message formed of a single hash value. It does not match the value of the second bit of the binary sequence of the digital watermark. P is this binary sequence of the second reference messages consistently transform. For this purpose, a single value of the least significant bit of the binary sequence of the second count of the message is changed to a zero value, as shown in figure 1(g). Hash is converted to a binary sequence of the second count of the message is zero, that is, coincides with the second bit of the binary sequence of the digital watermark. Then converted the binary sequence of the second reference message is passed to the recipient as a certified converted binary sequence of the second count of the message.

Let, as shown in figure 1(e), if the hash of the binary sequence of the k-th reference messages generated zero hash value. It does not match the value of the k-th bit of the binary sequence of the digital watermark. Therefore, the binary sequence of the k-th reference messages consistently transform. For this zero is the least significant bit of the binary sequence k-ro reference message is changed to a single value, as shown in figure 1(g). Hash is converted to a binary sequence of the k-th count of the message is zero, that is again not the same k-th bit of the binary sequence of the digital watermark. Then zero the penultimate (Phi is ur 1(d)) the most significant bit of the binary sequence of the k-th count of the message is changed to a single value, as shown in figure 1(and). Hash is converted so the binary sequence of the k-th count of the message is singular, i.e. coincides with the k-th bit of the binary sequence of the digital watermark. Then last converted binary sequence of the k-th reference message is passed to the recipient as certified.

The probability of mismatch hash value of the binary sequence of the next reference message from the i-th bit of the binary sequence of digital watermark is equal to ½. After conversion of the binary sequence of the next reference message by changing it to one of the least significant bits of the probability of mismatch resulting hash value is converted to a binary sequence of the next reference message from the i-th bit of the binary sequence of digital watermark is set to 1/4. After successive changes of one, two, three and so on to the least significant bits of the binary sequence of the next reference message conversion binary sequence of the next reference message, the probability of mismatch resulting hash value is converted to a binary sequence of the next reference message from the i-th bit of the binary sequence of digital watermark Rav is and 2^{
-η-1}where η - the number of consecutive modified least significant bits of the binary sequence of the next reference message. Choosing an appropriate value of the number η, you can almost guarantee a match hash values converted binary sequence of the next reference message from the i-th bit of the binary sequence of the digital watermark.

After certification of the binary sequence of the next reference message using the k-th bit of the binary sequence of digital watermark again, from the first to k-th, read the i-th bit of the binary sequence of the digital watermark, and the binary sequence of the next reference message and perform the subsequent action up until the coming of the binary sequence of the next timing messages. The number of binary sequences ordinary times, messages can be arbitrarily large. With the growth of its length in proportion to the number of the next group of k binary sequences of the next message counts, in each of which the recipient is authenticated the received message. Therefore, the longer the message, the more difficult it is for an attacker to change its contents or authorship. If the attacker divide the certified message into several parts, thanks assurance the sender of each group of k binary sequences of the next timing messages, the recipient of any part of the certified message length of at least k binary sequences ordinary times is able to validate its authenticity. Because the value of k is not more than tens of binary sequences, the attacker almost not able to separate notarized message, a length less than k binary sequences ordinary times, due to the fact that such short pieces of speech, sound, music, television, Fax, etc. messages do not carry relevant information for potential recipients.

The recipient of the message beforehand from among the received binary sequence of the next timing messages allocate count corresponding to the first bit of the binary sequence of the digital watermark from the sender of the message. For selecting the next reference message, corresponding to the first bit of the binary sequence of the digital watermark from the sender of the message, a pre-set maximum value of the probability P_{Osh}erroneous selection of this reference. The probability value P_{Osh}can be set, for example, of the order of 10^{-1}..10^{
-2}. If the errors of the transmission channel or a deliberate distortion of the certified message by an attacker, the recipient will not be able to allocate the count corresponding to the first bit of the binary sequence of the digital watermark from the sender of the message to the next group of k binary sequences of the next timing messages, the receiver will search for the required reference in the next group of k binary sequences ordinary times, messages and so on until until the desired count is selected. The probability of failure to make the required reference β successive groups of k binary sequences ordinary times, the message is P^{β} _{Osh}. As with the growing number β the probability of R^{β} _{Osh}very quickly approaches zero, there is provided a guaranteed allocation recipient of the next reference message, corresponding to the first bit of the binary sequence of the digital watermark from the sender of the message to a length of no more than β several successive groups of k binary sequences of the next timing of the message.

Adopted by the recipient of the binary sequence of the next timing messages hairout using a binary sequence a secret key in a tentative is but the generated hash functions. To hash with binary sequence a secret key in a pre-formed hash functions adopted by the binary sequence of the next reference message encrypts the data encryption algorithm DES-mode feedback text using the binary sequence of the secret key. The data encryption algorithm DES-mode feedback text using the binary sequence of the secret key are described, for example, in the book Mdeed, Dkent "the data encryption Standard: Past and future". TIER, 1988, - t, No. 5, page 49. Then the output value of length 64 bits of hash functions transform computation modulo 2.

Hashed values of the received binary sequence of the next message counts are compared sequentially with the appropriate, starting with the first, the values of the bits of the binary sequence of digital watermark before reaching m their matches in a row, where, a actionmeans rounding values-log_{2}P_{Osh}to the nearest integer, and the corresponding first bit of the binary sequence of the digital watermark from the sender of the message, take the first sample of m consecutive received binary sequence is of linesta regular counts of the messages.
Known methods of comparing hash values adopted by the binary sequence of the next reference message with the i-th bit of the binary sequence of digital watermark is described, for example, in the book: Writercon, Auldon "error-correcting Codes". M.: Mir, 1976, page 52.

Then the authentication is accepted by the recipient of the message consistently take k binary sequences of the next timing messages. Known methods of successive reception of k binary sequences of the next timing messages are described, for example, in the book Writercon, Auldon "error-correcting Codes". - M.: Mir, 1976, page 11.

Received binary sequence of the next timing messages hairout using a binary sequence a secret key in a pre-formed hash functions. To hash with binary sequence a secret key in a pre-formed hash functions adopted by the binary sequence of the next reference message encrypts the data encryption algorithm DES-mode feedback text using the binary sequence of the secret key. The data encryption algorithm DES-mode feedback text using the binary sequence Secretary the private key is described, for example, in the book Mdeed, Dkent "the data encryption Standard: Past and future". TIER, 1988, - t, No. 5, page 49. Then the output value of length 64 bits of hash functions transform computation modulo 2.

Each i-th hash value adopted by the binary sequence of the next reference message is compared with the i-th bit of the binary sequence of the digital watermark. Known methods of comparison of each i-th hash value with the i-th bit of the binary sequence of digital watermark is described, for example, in the book: Writercon, Auldon "error-correcting Codes". - M.: Mir, 1976, page 52. The result of the comparison values may be their match or mismatch.

Calculate the number of K_{with}hashed binary sequences ordinary times, the message of the k received samples, which coincided with the values of corresponding bits of the binary sequence of the digital watermark. The number of K_{c}calculated as the arithmetic sum of the cases matches the hashed binary sequences ordinary times, the message of the k received samples with the values of corresponding bits of the binary sequence of the digital watermark. The calculated value of K_{c}may be in the range from zero to k, inclusive.

While performing at the conditions_{
c}≥_{min}taken k binary sequences ordinary times, the message is considered authentic. Failure to carry out this inequality the authenticity of the received k binary sequences is not confirmed.

Let, as shown in figure 4(e), authenticates the received k binary sequences of the next timing messages. Hash value adopted by the binary sequence of the first reference message, shown in figure 4(g)coincides with the value of the first bit of the binary sequence of the digital watermark, so the number of K_{with}installed in a single value:_{c}=1, as shown in figure 4(C).

Similarly processed the following k-1 received binary sequence of the next timing messages. Let, as shown in figure 4(C), after taking k binary sequences ordinary times, the message is the condition To_{c}≥_{min}. Therefore, taken k binary sequences ordinary times, the message is considered authentic, as shown in figure 4(and).

Then repeat the steps for authentication of the next group of k binary sequences ordinary times, messages and so on until completion of reception of all binary sequences of the next timing messages. If the test is truly the ti are all taken by k binary sequence of the next timing messages recognized as genuine, all received message is considered authentic.

Verification of theoretical assumptions of the claimed method of forming and verifying digitally watermarked message was checked by analytical studies.

The probability of making a genuine group of k regular counts of messages that are authentic, equal. The figure 5 shows the dependence of P_{Nepal}from the values of K_{min}. From figure 5 it is seen that the minimum number of K_{min}must be installed such that ran P_{Nepal}≤P_{SS}.

Studies show that using the proposed method of generating and verifying digitally watermarked messages are enhanced its security to the deliberate actions of intruders to modify the message content and authorship.

1. Method of generating and verifying digitally watermarked message, namely, that previously to the sender and the receiver form a binary sequence of digital watermark length of k bits and a bit string of the secret key to verify the sender of the message using binary sequences of digital watermark and secret key, re is indicate the certified message to the recipient,
where authenticates the received message using binary sequences of digital watermark and secret key, characterized in that it further previously for the sender and receiver form a hashing function with a binary output value and set the minimum number of K_{min}authentic samples of messages within a group of k consecutive received, assurances from the sender of the message sequentially reads the i-th, where i=1, 2,...,k-bit binary sequence of digital watermark and the binary sequence of the next reference message, which hairout using a binary sequence a secret key in a pre-formed hash functions, and then compare the hash value with the i-th bit of the binary sequence of the digital watermark, and when they match the binary sequence of the next reference message is passed to the recipient as certified, and if not binary sequence of the next reference message consistently transform by change bits, then after every conversion, the converted binary sequence of the next reference message hairout using the binary sequence of the secret key is a pre-generated hash functions,
compare the hash value with the i-th bit of the binary sequence of the digital watermark, and converting the binary sequence of the next reference message perform to match the hash values of the converted binary sequence of the next reference message with the i-th bit of the binary sequence of the digital watermark, and then converted to a binary sequence of the next reference message is passed to the recipient as certified, and upon the certification of the binary sequence of the next reference message using the k-th bit of the binary sequence of digital watermark again, from the first to k-th, read the i-th bit of the binary sequence of the digital watermark and binary the sequence of the next reference message and perform the subsequent action up until the coming of the binary sequence of the next timing of the message, and the recipient of the message beforehand from among the received binary sequence of the next timing messages allocate count corresponding to the first bit of the binary sequence of the digital watermark from the sender of the message, then the authentication is accepted by the recipient of the message consistently Ave is NIMA k binary sequences of the next timing messages
hairout them using a binary sequence a secret key in a pre-formed hash functions and each i-e a hash value is compared with the i-th bit of the binary sequence of the digital watermark, compute the number of K_{c}hashed binary sequences ordinary times, the message of the k received samples, which coincided with the values of corresponding bits of the binary sequence of the digital watermark, and when K_{c}≥_{min}taken k binary sequences ordinary times, the message is considered authentic, and then repeat the steps for authentication of the next group of k binary sequences ordinary times, messages and so on until completion of reception of all binary sequences of the next timing of the message.

2. The method according to claim 1, characterized in that for the conversion of the binary sequence of the next reference message by changing the bits sequentially change it one, two, three and so on to the least significant bits.

3. The method according to claim 1, characterized in that the minimum number of K_{min}authentic samples of messages within a group of k consecutive received set of conditionswhere P_{under}allowable probability of acceptance under the ina group of k regular counts of the messages,
which is not true.

4. The method according to claim 1, characterized in that the selection of the next reference message, corresponding to the first bit of the binary sequence of the digital watermark from the sender of the message, a pre-set maximum value of the probability P_{Osh}erroneous selection of reference adopted by the recipient of the binary sequence of the next timing messages hairout using a binary sequence a secret key in a pre-formed hash functions, hashed values are compared sequentially with the appropriate, starting with the first, the values of the bits of the binary sequence of digital watermark before reaching m their matches in a row, whereand the actionmeans rounding values-log_{2}P_{Osh}to the nearest integer, and the corresponding first bit of the binary sequence of the digital watermark from the sender of the message take the first sample of k consecutive received binary sequence of the next timing of the message.

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FIELD: information protection.

SUBSTANCE: method for transferring messages while providing for confidentiality of identification signs of communication system objects with interaction of devices of communication system subscribers through central device for each communication session cryptographic conversion of subscriber device identifier is performed using encryption key of current subscriber device, while during said cryptographic conversion symmetrical cryptographic algorithm is used and two message transfer modes are taken in consideration, on initiative from subscriber device to central device and vice versa.

EFFECT: protection from unsanctioned access to identifiers of devices of system subscribers transferred via communication channels, in particular when providing for confidentiality of messages identification signs in communications systems with multiple subscriber devices.

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FIELD: cryptography.

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EFFECT: higher speed and efficiency.

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FIELD: computer science.

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EFFECT: higher efficiency, broader functional capabilities.

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FIELD: data carriers.

SUBSTANCE: device has calculating, reserving and recording modules. Each variant of semiconductor memory card contains area for recording user data for controlling volume and area for recording user data. On carrier method for computer initialization is recorded, including calculation of size of volume control information, reserving areas and recording therein of control information for volume and user data, recording main boot record and sectors table in first section of first area, skipping preset number of sectors, recording information of boot sector of section, file allocation table and root directory element to following sectors.

EFFECT: higher efficiency.

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EFFECT: higher reliability, higher efficiency.

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FIELD: computer science.

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